A. Field of the Invention
The field of the present invention relates generally to support mats configured to allow load bearing objects, such as a vehicle or pedestrian traffic to move over turf areas without significant compaction or other damage to the turf. More particularly, the present invention relates to such support mats that comprise a plurality of upstanding, open cell members configured for turf to grow through the mat. Even more particularly the present invention relates to such support mats that are rollable for ease of storage, delivery and installation.
B. Background
As well known to those in the turf and paving industries, there are numerous circumstances when it is necessary or desirable to be able to drive vehicles over turf areas, such as grassy or like areas, instead of the typical asphalt, concrete or other solid materials normally used as the load bearing material for roadways or vehicle pathways. Driving vehicles of any substantial weight or at any speeds other than at very low speeds over a turf area can easily result in substantial damage to the turf, particularly if the turf area is wet or configured with turf that is particularly susceptible to damage. Despite the potential for damage to the turf, driving vehicles over the turf occurs out of necessity when the turf area is used for temporary or overflow parking, to temporarily connect different parking areas and to permit temporary access across the turf to facilities or for various emergency situations. Allowing vehicles to drive over turf areas is desirable when, often for aesthetic purposes or to avoid interfering with the purpose of the turf area (i.e., golf courses), the owners or operators of the turf areas prefer to not have paths made up of the typical solid roadway materials cutting across the turf area, thereby dividing the turf area into disconnected segments. Examples of turf areas where the use of standard roadway materials are often not desired include golf cart paths, service roads through or overflow parking areas in parks and other park-like areas, residential driveways, emergency vehicle access lanes, grass air strips and the like. As well known, movement of vehicles across the turf can result in ruts in the turf, tearing of the turf and undesirable compaction of the turf and/or soil underneath that can inhibit or prevent normal turf growth.
To prevent damage to the turf from the movement of vehicles, such as cars, trucks, golf carts, emergency vehicles and other such vehicles, across or through the turf area it is common to utilize load bearing mats embedded or otherwise placed in or on the turf. Commonly, these load bearing mats are made up of a plurality of individual mat units and generally configured with a plurality of connected cell or cell-like members that are of sufficient strength to support the weight of the vehicle or other load bearing traffic as it moves over the turf. Many of the load bearing mats have cell members that are configured, at least to a certain extent, to allow the turf to grow through the load bearing mat and to allow water and other nutrients to reach the roots of the turf. The load bearing mats are typically placed in the turf or soil base just below the grade level of the turf so that conventional turf equipment, including lawnmowers and the like, can move over the turf and cut or treat the turf. To allow for different sizes of areas where load bearing mats are utilized, the typical load bearing mat is provided in modular mat units that can be selectively connected together to provide the desired amount of load bearing surface (i.e., parking lot sized area). The area enclosed by the cell members are filled with soil or other materials. In turf areas, the fill material preferably comprises that which facilitates the growth of turf through the load bearing mat. To facilitate gripping of the subsurface by the load bearing mat, drainage through the turf and oxygen transfer by the turf, it is generally desirable that the base of the individual cell members have as much opening as possible.
The use of load bearing mats to provide support in turf areas is not limited to use with areas where vehicles may move across or through the turf area. In addition, load bearing mats are also utilized in areas subject to heavy pedestrian or other non-vehicle load bearing traffic, such as for walking and/or bicycle paths through a park or park-like settings. Use of load bearing mats are also beneficially utilized on campus open areas where students are likely to cut across the turf and in areas around nursing homes or hospitals where persons may want to push another person in a wheelchair or use other equipment. Use of load bearing mats to prevent damage to turf is known to be particularly advantageous in areas where water or other fluids may commonly collect after watering or rain.
Examples of load bearing mats for use in turf areas can be found in numerous prior art patents. For instance, U.S. Pat. No. 4,621,942 to Hill describes a grass paving structure having a plurality of honeycombed, hexagon-shaped cells with upstanding sidewalls and a plurality of openings in the underlying base surface. In one configuration, as sold by National Diversified Sales, Inc. (the assignee of the present invention) under the name Tufftrack Grassroad Pavers, the load bearing members are sold in two foot by two foot interlocking sections that can be connected together to cover any size of area. A tongue and groove latching system provides quick and secure connections between the various sections. U.S. Pat. No. 4,111,585 to Mascaro describes a modular support mat for turfgrass areas that has a plurality of hexagonally shaped, adjoining cells that form a module of such cells. Individual modules are joined together by the use of selectively positioned integral projecting tabs having upstanding lugs thereon that are adapted to interlockingly engage a correspondingly located opening in an adjacent modular unit. U.S. Pat. No. 5,250,340 to Bohnhoff describes a mat for stabilizing particulate materials that comprises a planar quadrilateral grid formed by a plurality of intersecting struts having upstanding tubular members disposed on the grid in a rectangular array. This mat, sold as the Grasspave2 by Invisible Structures, Inc. out of Golden, Colo., utilizes perpendicularly disposed struts that intersect at the bottom center of each tubular member and a socket/pin connector system to connect mats together to form a larger mat. The use of ribs between spaced apart tubular members allows the mat, or a series of interconnected mats, to be rolled. U.S. Pat. No. 5,102,048 to Bohnhoff describes a irrigation head support that includes a circular mat having a plurality of concentric circular ribs and radially disposed ribs with a centrally located circular aperture configured to receive an irrigation head and a plurality of upstanding tubular rings on the mat around the circular aperture. The tubular rings provide support for vehicle tires and other loads so as to avoid damage to the irrigation head. Grass roots grow through the spaces in the mat to secure the mat permanently in place.
The presently available load bearing mats generally comprise a plurality of cell or tubular shaped members that are configured in a generally honeycombed fashion, such as illustrated by U.S. Pat. No. 4,111,585 to Mascaro set forth above. These honeycombed configured mats obtain much of their load bearing strength due to the fact that the cell members share common sidewalls or, at a minimum, abutting sidewalls. While the interconnecting or abutting cell sidewalls provide strength for somewhat significant loads, the resulting load bearing mat must be configured from a plurality of individual generally rigid panels or mat units that are not very well adapted to being rolled. These flat panels are generally stored, transported and installed in their separate panel condition instead of a preferred rolled condition. As known to those skilled in the art, handling and installation of mats or mat-like structures such as load bearing mats is generally made significantly easier, faster and less expensive if the mat is provided in a rolled condition that can be unrolled into place where needed. As also set forth above, U.S. Pat. No. 5,250,340 to Bohnhoff describes a load bearing mat that comprises a plurality of cell members placed on at planar grid, thereby making it suitable for being provided in a rolled condition. In that configuration, however, the grid members that make up the grid cross at intersections located at or near the center of the cell members. The grids and intersection thereof at the center of the cell members somewhat reduces the amount of open area in the cell member that is available for horticultural purposes, namely the growth of turf or other plant material. While the rolled ability of this grid does provide installation labor and costs savings versus rigid panels, the loss of area available for plant growth is seen by many in the industry as a limitation to this type of load bearing unit.
The area to be covered by load bearing units is generally a variable that must be addressed by those who manufacture and supply load bearing mats. The typical manner in which this is addressed is by providing the load bearing mats in individual panels or mat units. To effectively cover the desired area, it is preferred that the individual panels be configured to lock together to form a substantially integral load bearing mat. The honeycomb configured load bearing mats typically utilize connecting mechanisms that connect cells of one panel to cells of an adjacent panel in an abutting relationship. During installation, the user connects these panels together to form the desired size of load bearing mat. With regard to load bearing mats provided in a rolled condition, a series of panels can be connected together to form a roll of such panels having a specified width. However, the connecting mechanism must be configured to allow and adapt to the rolling and unrolling of the mat. The mat described in U.S. Pat. No. 5,250,340 and sold by Invisible Structures, Inc. utilizes a pin and socket type of connecting mechanism that is configured in a generally vertical or axial manner. In use, this type of connecting mechanism can result in dimpling of the leveled planting base during installation and tends to unsnap during and after installation due to vertically applied loads. What is needed, therefore, is a rollable load bearing mat that is configured for use as a load bearing surface in turf areas that includes the use of interconnected cell members for mat strength, the ability to provide the mat in a rolled condition for ease of handling and installation, and the use of mat unit connectors that are suitable for rolling and which do not have the problems associated with vertically or axially configured pin and socket connectors.